Washington, United States (AFP) February 26 - Three major international news wire agencies on Wednesday called steps by the White House to limit their access to the pool covering President Donald Trump a threat to the independence of the press.

On Tuesday, the White House stripped journalists of the nearly century-old power to decide which of them cover US presidential events, with Trump boasting that he was now "calling those shots" on media access.

"It is essential in a democracy for the public to have access to news about their government from an independent, free press," said a statement signed by the editorial heads of Reuters, Bloomberg News and The Associated Press.

"We believe that any steps by the government to limit the number of wire services with access to the President threatens that principle."

The press pool is a small group of reporters that covers the US president in cramped spaces, particularly the Oval Office, and shares their material with other news organizations.

The three agencies, which had permanent seats as part of the White House pool in the past, have seen that access reduced to a single seat under the new policy.

The Associated Press, which Trump has barred from presidential events in a row over his renaming the Gulf of Mexico as the "Gulf of America," has seen its access to presidential events revoked completely.

In their statement, the agencies said the move "harms the spread of reliable information to people, communities, businesses and global financial markets that heavily depend on our reporting."

The statement was signed by AP Executive Editor Julie Pace, Bloomberg Editor-in-Chief John Micklethwait and Reuters Editor-in-Chief Alessandra Galloni.

Before the White House announcement, members of the pool were chosen by the White House Correspondents Association, an independent group representing journalists.

AFP is also part of the White House pool, but is in a different category to AP, Bloomberg and Reuters. Its access has not been altered by the recent changes by the Trump administration.

Katherine Jacobsen, program coordinator with watchdog Committee to Protect Journalists (CPJ), told AFP "solidarity among news organizations" was crucial when faced with such challenges.

"This is not a partisan issue, this is not a left-leaning media issue or a right-leaning media issue," she said.

"This is an issue of access to information and the state of American democracy and what does it say if one of the world's largest wire agencies is not able to access pool information at the White House."